scholarly journals Recapitulation of the Sexual Cycle of the Primary Fungal Pathogen Cryptococcus neoformans var. gattii: Implications for an Outbreak on Vancouver Island, Canada

2003 ◽  
Vol 2 (5) ◽  
pp. 1036-1045 ◽  
Author(s):  
James A. Fraser ◽  
Ryan L. Subaran ◽  
Connie B. Nichols ◽  
Joseph Heitman
Keyword(s):  
Cryptococcus Neoformans ◽  
Fungal Pathogen ◽  
Large Scale ◽  
Vancouver Island ◽  
Sexual Cycle ◽  
Gene Encoding ◽  
Tropical Regions ◽  
Human Fungal Pathogen ◽  
Large Scale Analysis ◽  
Serotype B

ABSTRACT Cryptococcus neoformans is a human fungal pathogen that exists as three distinct varieties or sibling species: the predominantly opportunistic pathogens C. neoformans var. neoformans (serotype D) and C. neoformans var. grubii (serotype A) and the primary pathogen C. neoformans var. gattii (serotypes B and C). While serotypes A and D are cosmopolitan, serotypes B and C are typically restricted to tropical regions. However, serotype B isolates of C. neoformans var. gattii have recently caused an outbreak on Vancouver Island in Canada, highlighting the threat of this fungus and its capacity to infect immunocompetent individuals. Here we report a large-scale analysis of the mating abilities of serotype B and C isolates from diverse sources and identify unusual strains that mate robustly and are suitable for further genetic analysis. Unlike most isolates, which are of both the a and α mating types but are predominantly sterile, the majority of the Vancouver outbreak strains are exclusively of the α mating type and the majority are fertile. In an effort to enhance mating of these isolates, we identified and disrupted the CRG1 gene encoding the GTPase-activating protein involved in attenuating pheromone response. crg1 mutations dramatically increased mating efficiency and enabled mating with otherwise sterile isolates. Our studies provide a genetic and molecular foundation for further studies of this primary pathogen and reveal that the Vancouver Island outbreak may be attributable to a recent recombination event.

Evidence for genetic incompatibilities associated with post-zygotic reproductive isolation in the human fungal pathogen Cryptococcus neoformans

Genome ◽  
2014 ◽  
Vol 57 (6) ◽  
pp. 335-344 ◽  
Author(s):  
Aaron A. Vogan ◽  
Jianping Xu
Keyword(s):  
Reproductive Isolation ◽  
Cryptococcus Neoformans ◽  
Segregation Distortion ◽  
Fungal Pathogen ◽  
Fungal Pathogens ◽  
Large Scale ◽  
Hybrid Progeny ◽  
Epistatic Interactions ◽  
Human Fungal Pathogen ◽  
Hybrid Cross

Hybridization is a potent mechanism for generating unique strains with broad host ranges and increased virulence in fungal pathogens. In the opportunistic basidiomycete pathogen Cryptococcus neoformans, intervarietal hybrids are commonly found infecting patients. The two parental varieties C. neoformans var. grubii and C. neoformans var. neoformans mate readily under laboratory conditions, but the hybrid basidiospores have germination rates about four times lower than those from intravarietal crosses. Here, we used microdissection to collect basidiospores from a hybrid cross and analysed the genotypes of germinated basidiospores to identify potentially antagonistic allelic combinations between loci that impact basidiospore germination. Our analyses showed clear evidence for Bateson–Dobzhansky–Muller (BDM) incompatibility affecting basidiospore viability. Antagonistic combinations of alleles from both two loci and three loci were found. Interestingly, most of the hybrid progeny showed segregation distortion in favour of the alleles from var. neoformans, consistent with large-scale epistatic interactions among loci affecting basidiospore viability. Our study presents the first evidence of BDM incompatibility between nuclear genes affecting post-zygotic reproductive isolation in this model basidiomycete yeast.

Broadening the spectrum of fluorescent protein tools for use in the encapsulated human fungal pathogen Cryptococcus neoformans

2020 ◽  
Vol 138 ◽  
pp. 103365
Author(s):  
Garrick W.K. Spencer ◽  
Sheena M.H. Chua ◽  
Paige E. Erpf ◽  
Maha S.I. Wizrah ◽  
Taylor G. Dyba ◽  
...  
Keyword(s):  
Cryptococcus Neoformans ◽  
Fungal Pathogen ◽  
Fluorescent Protein ◽  
Human Fungal Pathogen

scholarly journals Erg6 affects membrane composition and virulence of the human fungal pathogen Cryptococcus neoformans

2020 ◽  
Vol 140 ◽  
pp. 103368 ◽  
Author(s):  
Fabiana Freire M. Oliveira ◽  
Hugo Costa Paes ◽  
Luísa Defranco F. Peconick ◽  
Fernanda L. Fonseca ◽  
Clara Luna Freitas Marina ◽  
...  
Keyword(s):  
Cryptococcus Neoformans ◽  
Fungal Pathogen ◽  
Membrane Composition ◽  
Human Fungal Pathogen

scholarly journals Sex-Specific Homeodomain Proteins Sxi1α and Sxi2a Coordinately Regulate Sexual Development in Cryptococcus neoformans

2005 ◽  
Vol 4 (3) ◽  
pp. 526-535 ◽  
Author(s):  
Christina M. Hull ◽  
Marie-Josee Boily ◽  
Joseph Heitman
Keyword(s):  
Cryptococcus Neoformans ◽  
Sexual Development ◽  
Expression Patterns ◽  
Regulatory Protein ◽  
Control Cell ◽  
Sexual Cycle ◽  
Homeodomain Protein ◽  
Homeodomain Proteins ◽  
Human Fungal Pathogen ◽  
Cell Type Specific

ABSTRACT Homeodomain proteins are central regulators of development in eukaryotes. In fungi, homeodomain proteins have been shown to control cell identity and sexual development. Cryptococcus neoformans is a human fungal pathogen with a defined sexual cycle that produces spores, the suspected infectious particles. Previously, only a single homeodomain regulatory protein involved in sexual development, Sxi1α, had been identified. Here we present the discovery of Sxi2a, a predicted but heretofore elusive cell-type-specific homeodomain protein essential for the regulation of sexual development. Our studies reveal that Sxi2a is necessary for proper sexual development and sufficient to drive this development in otherwise haploid α cells. We further show that Sxi1α and Sxi2a interact with one another and impart similar expression patterns for two key mating genes. The discovery of Sxi2a and its relationship with Sxi1α leads to a new model for how the sexual cycle is controlled in C. neoformans, with implications for virulence.

scholarly journals Relative Contributions of Prenylation and Postprenylation Processing in Cryptococcus neoformans Pathogenesis

mSphere ◽  
2016 ◽  
Vol 1 (2) ◽  
Author(s):  
Shannon K. Esher ◽  
Kyla S. Ost ◽  
Lukasz Kozubowski ◽  
Dong-Hoon Yang ◽  
Min Su Kim ◽  
...  
Keyword(s):  
Subcellular Localization ◽  
Cryptococcus Neoformans ◽  
Posttranslational Modification ◽  
Fungal Pathogen ◽  
Content Type ◽  
Processing Enzymes ◽  
Human Fungal Pathogen ◽  
Modification Process ◽  
Substrate Proteins ◽  
Processing Steps

ABSTRACT Cryptococcus neoformans is an important human fungal pathogen that causes disease and death in immunocompromised individuals. The growth and morphogenesis of this fungus are controlled by conserved Ras-like GTPases, which are also important for its pathogenicity. Many of these proteins require proper subcellular localization for full function, and they are directed to cellular membranes through a posttranslational modification process known as prenylation. These studies investigate the roles of one of the prenylation enzymes, farnesyltransferase, as well as the postprenylation processing enzymes in C. neoformans. We demonstrate that the postprenylation processing steps are dispensable for the localization of certain substrate proteins. However, both protein farnesylation and the subsequent postprenylation processing steps are required for full pathogenesis of this fungus. Prenyltransferase enzymes promote the membrane localization of their target proteins by directing the attachment of a hydrophobic lipid group at a conserved C-terminal CAAX motif. Subsequently, the prenylated protein is further modified by postprenylation processing enzymes that cleave the terminal 3 amino acids and carboxymethylate the prenylated cysteine residue. Many prenylated proteins, including Ras1 and Ras-like proteins, require this multistep membrane localization process in order to function properly. In the human fungal pathogen Cryptococcus neoformans, previous studies have demonstrated that two distinct forms of protein prenylation, farnesylation and geranylgeranylation, are both required for cellular adaptation to stress, as well as full virulence in animal infection models. Here, we establish that the C. neoformans RAM1 gene encoding the farnesyltransferase β-subunit, though not strictly essential for growth under permissive in vitro conditions, is absolutely required for cryptococcal pathogenesis. We also identify and characterize postprenylation protease and carboxyl methyltransferase enzymes in C. neoformans. In contrast to the prenyltransferases, deletion of the genes encoding the Rce1 protease and Ste14 carboxyl methyltransferase results in subtle defects in stress response and only partial reductions in virulence. These postprenylation modifications, as well as the prenylation events themselves, do play important roles in mating and hyphal transitions, likely due to their regulation of peptide pheromones and other proteins involved in development. IMPORTANCE Cryptococcus neoformans is an important human fungal pathogen that causes disease and death in immunocompromised individuals. The growth and morphogenesis of this fungus are controlled by conserved Ras-like GTPases, which are also important for its pathogenicity. Many of these proteins require proper subcellular localization for full function, and they are directed to cellular membranes through a posttranslational modification process known as prenylation. These studies investigate the roles of one of the prenylation enzymes, farnesyltransferase, as well as the postprenylation processing enzymes in C. neoformans. We demonstrate that the postprenylation processing steps are dispensable for the localization of certain substrate proteins. However, both protein farnesylation and the subsequent postprenylation processing steps are required for full pathogenesis of this fungus.

scholarly journals Molecular Mechanisms of Hypoxic Responses via Unique Roles of Ras1, Cdc24 and Ptp3 in a Human Fungal Pathogen Cryptococcus neoformans

PLoS Genetics ◽  
2014 ◽  
Vol 10 (4) ◽  
pp. e1004292 ◽  
Author(s):  
Yun C. Chang ◽  
Ami Khanal Lamichhane ◽  
H. Martin Garraffo ◽  
Peter J. Walter ◽  
Maarten Leerkes ◽  
...  
Keyword(s):  
Cryptococcus Neoformans ◽  
Fungal Pathogen ◽  
Molecular Mechanisms ◽  
Human Fungal Pathogen

scholarly journals Elucidation of the determinant for orchestration of solo unisexual cycle in an important human fungal pathogen

2019 ◽  
Author(s):  
Pengjie Hu ◽  
Huimin Liu ◽  
Lei Chen ◽  
Guang-Jun He ◽  
Xiuyun Tian ◽  
...  
Keyword(s):  
Sex Determination ◽  
Sexual Development ◽  
Fungal Pathogen ◽  
Model Organism ◽  
Sexual Cycle ◽  
Critical Determinant ◽  
Human Fungal Pathogen ◽  
Alternative Approach ◽  
Sexual Determination ◽  
Functional Profiling

AbstractIn fungi, the sex-determination program universally directs sexual development and syngamy (the fusion of gametes) that underlies pre-meiotic diploidization. However, the contribution of sex-determination to syngamy-independent sexual cycle, which requires autopolyploidization as an alternative approach to elevate ploidy before meiosis, remains unclear in fungi and other eukaryotes. The human fungal pathogen Cryptococcus neoformans, as a model organism for studying fungal sexual reproduction, can undergo syngamy-dependent bisexual and syngamy-independent solo unisexual reproduction, in which endoreplication is considered to enable pre-meiotic self-diploidization. Here, by characterizing a mutant lacking all the core sex-determination factors, we show that sex-determination plays a central role in bisexual syngamy but is not strictly required for unisexual development and self-diploidization. This implies an unknown circuit, rather than the sex-determination program, for specifically coordinating Cryptococcus unisexual cycle. We reveal that syngamy and self-diploidization are both governed by the Qsp1-directed paracrine system via two regulatory branches, Vea2 and Cqs2. Vea2 directs bisexual syngamy through the sex-determination program; conversely, Cqs2 is dispensable for bisexual syngamy but activates unisexual endoreplication. Through functional profiling of 41 transcription factors documented to regulate Cryptococcus sexual development, we reveal that only Cqs2 can drive and integrate all unisexual phases and ensure the production of meiospore progenies. Furthermore, ChIP-seq analysis together with genetic evaluation indicate that Cqs2 induces unisexual self-diploidization through its direct control of PUM1, whose expression is sufficient to drive autopolyploidization. Therefore, Cqs2 serves as the critical determinant that orchestrates Cryptococcus multistage unisexual cycle that does not strictly require the sexual-determination program.

scholarly journals Genetic and environmental influences on the evolution of virulence in the HIV-associated opportunistic human fungal pathogen Cryptococcus neoformans

2021 ◽  
Author(s):  
Yiwu Yu ◽  
Yuanyuan Wang ◽  
Linghua Li ◽  
Xiaoqing Chen ◽  
Xinhua Huang ◽  
...  
Keyword(s):  
Cryptococcus Neoformans ◽  
Natural Environment ◽  
Large Scale ◽  
Sequence Type ◽  
Sequencing Analysis ◽  
Uninfected Individual ◽  
Human Fungal Pathogen ◽  
Virulence Evolution ◽  
Capsule Production ◽  
Genetic And Environmental Factors

The fungus Cryptococcus neoformans is considered the leading cause of death in immunocompromised patients. Despite numerous investigations concerning its molecular epidemiology, there are only a few studies addressing the impacts of varying factors on genotype-phenotype correlations. It remains largely unknown whether genetic and environmental variabilities among isolates from different sources may have dramatic consequences on virulence. In this study, we analyzed 105 Chinese C. neoformans isolates, including 54 from HIV-infected patients, 44 from HIV-uninfected individuals and 7 from a natural environment, to investigate factors influencing the outcome of C. neoformans infection. MLST analysis clearly identified sequence type (ST) 5 as the prevalent sequence type in all clinical isolates and interestingly, genotypic diversities were observed in isolates from both HIV-uninfected individual and natural environment but not those from HIV-infected patients. Moreover, we found that compared to those from HIV-infected patients, the isolates from HIV-uninfected individuals exhibited enhanced virulence-associated traits including significantly elevated capsule production and melanin formation, increases in survival in human cerebrospinal fluid (CSF), less effective uptake by host phagocytes, and higher mortality in a mouse model of cryptococcosis. Consistently, pathogenic phenotypes were associated with CD4 counts of patients, implying environmental impact on within-host C. neoformans virulence. Importantly, a large-scale whole-genome sequencing analysis revealed that genomic variations within genes related to specific functions may act as a vital driving force of host intrinsic virulence evolution. Taken together, our results support a strong genotype-phenotype correlation suggesting that the pathogenic evolution of C. neoformans could be heavily affected by both genetic and environmental factors.

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